Cutting ring element for a centrifugal chopper pump

ABSTRACT

A cutting ring element for a centrifugal pump of the chopper type comprises a ring-like structure having at least one cutting member positioned along the ring-like structure and extending outwardly therefrom. The cutting ring element is structured to be positioned adjacent the drive side of an impeller having cutting structures associated with the drive side of the impeller which interact with the cutting ring element to chop and reduce the size of entrained solids in a pumped fluid, or slurry, to prevent such solids from infiltrating behind the impeller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to centrifugal pumps of the type known as chopperpumps, which are structured to process fluids containing large-sizedsolids that must be cut or chopped by the pump. Specifically, thisinvention relates to a cutting ring element which is configured to workin tandem with an appropriately configured impeller to process entrainedsolids and exclude them from the rear portion of the impeller, and thusthe seal of the pump.

2. Description of Related Art

Centrifugal pumps of the chopper type are used in many and variedindustries to process fluids that contain larger-sized solids, such asplastics or animal byproducts. Chopper pumps are typically characterizedby having an impeller that is structured to contact a cutting elementpositioned adjacent the vanes of the impeller to exert a cutting orchopping action on the solid material entering the pump. The impellerand cutting structures positioned on the suction side of chopper pumpsprocess the majority of the solids content to a size that can be movedthrough the pump. However, some solids tend to also move toward thedrive side, or back, of the impeller and may move inwardly toward thedrive shaft of the pump.

When solids move toward the drive side, or back, of the impeller andinwardly toward the drive shaft, debris can become wrapped around thedrive shaft and impede the operation of the pump. This is especially thecase with fluids containing stringy solids. Debris behind the impellercan cause a build up in heat and wear on the impeller and can impede thecooling and lubrication of the seal elements. Solid material mayinfiltrate the seal and cause further problems with pump operation.Thus, some known chopper pumps have employed flushing mechanisms toclean behind the impeller.

Other known chopper pumps have used impellers designed with cuttingelements located on or near the back side of the impeller and about thedrive shaft to chop solid material in the location of the drive shaft.An example of an impeller and cutting element of the type described isdisclosed in U.S. Pat. No. 5,460,482 to Dorsch. Some chopper pumps alsouse restrictor bushings around the shaft to keep larger solids away fromthe seal, as described in the '482 patent to Dorsch. Yet other chopperpumps use an open impeller design to reduce pressure behind the impellerso that solids are not drawn toward the back side of the impeller.

Prior art chopper pumps which employ a cutting element on the back sideof the impeller require that the cutting element be positioned adjacentthe impeller hub and/or in very close proximity to the drive shaft. Assuch, debris in the fluid, especially stringy material, can infiltrateall the way to the drive shaft and seal assembly before any chopping orcutting of the material takes place.

Thus, it would be advantageous in the art to provide an impeller andcutting element configuration in a centrifugal chopper pump thatprocesses and excludes debris from behind the impeller before the debriscan reach the drive shaft and seal assembly, thereby improving pumpoperation and the life of the pump. Co-pending U.S. application Ser. No.10/893,506, which is commonly owned with the present application,discloses an impeller and cutting elements that are configured tointeract in a manner that chops or cuts debris near the peripheral edgeof the drive side of the impeller to effectively reduce and excludedebris from contact with the drive shaft and any associated sealingassemblies

While the impeller and cutting elements disclosed in U.S. applicationSer. No. 10/893,506 are particularly suitable for their intendedpurpose, the configuration of the cutting elements is such that theindividual cutting elements must be replaced individually when worn. Itwould be advantageous, therefore, to provide a more simplified andcost-effective configuration for the cutting elements located tointeract on the drive side of the impeller.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a cutting ring element isprovided for use in chopper type centrifugal pumps and is configured forpositioning relative to the impeller of the pump to interact in a mannerthat chops or cuts debris near the peripheral edge of the drive side ofthe impeller to effectively reduce and exclude debris from contact withthe drive shaft and any associated sealing assemblies. While the cuttingring element of the present invention is described herein with respectto use in centrifugal pumps of the chopper type, the cutting ringelement may be adapted for use in types of centrifugal pumps other thanchopper pumps.

The present invention comprises a cutting ring element that isconfigured for positioning in a centrifugal pump adjacent to the driveside of the impeller to interact with cutting structures that are formedon the drive side of the impeller. An impeller of the type described,for use in chopper pumps, is disclosed in co-pending application Ser.No. 10/893,506, the content and disclosure of which are incorporatedherein by reference. The impeller, having a drive side oriented awayfrom the inlet of the pump, is particularly configured with cuttingstructures that interact with the cutting ring element of the presentinvention. The cutting structures on the drive side of the impeller, andwith which the cutting ring element of the present invention interact,are positioned toward the outer periphery of the impeller to providechopping and cutting of solids near the periphery of the impeller. Theperipherally-located cutting structures of the impeller are particularlypositioned to exclude the chopped debris from the drive side of theimpeller, and especially away from the drive shaft and any associatedsealing assemblies.

The cutting ring element of the present invention is formed generally asa continuous ring-like structure that has positioned on the ring andextending outwardly therefrom at least one cutting member sized andconfigured to interact with a cutting structure positioned on animpeller. The cutting member may be of any suitable size, shape orconfiguration to interact with the particularly sized, shaped orconfigured cutting structures of the impeller. In one embodiment of theinvention, a plurality of cutting members are positioned on thering-like structure.

The cutting ring element of the present invention is positioned in acentrifugal pump adjacent the drive side of the impeller. The cuttingring element may be structured, therefore, to be positioned against andsecured to the pump casing so as to be adjacently positioned next to theimpeller. Alternatively, and as described more particularly herein, thecutting ring element may be configured for attachment to a separate backplate that is, in turn, positioned between the pump casing and the driveside of the impeller. Providing the adjacently positioned cutting ringelement on a separate plate-like structure, attachable to and separatefrom the pump casing, has the particular advantage of providing axialadjustment of the cutting ring element relative to the impeller and wheninstallation of the cutting ring element is made as a retrofit to anexisting pump. In either construction, however, the ring-likeconstruction of the cutting ring element facilitates the removal andreplacement of the cutting member or members when worn due to extendeduse, and avoids the need to replace individual cutting structures as ispresently known in the prior art. The construction of the ring-likemember and cutting member or members is more cost-effective as well.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate what is currently considered to be thebest mode for carrying out the invention

FIG. 1 is a view in longitudinal cross section of a centrifugal pump ofthe chopper type illustrating an exemplar installation of the cuttingring element of the present invention;

FIG. 2 is a perspective view of the cutting ring element of the presentinvention;

FIG. 3 is a plan view of the cutting ring element shown in FIG. 2;

FIG. 4 is a view in cross section of the cutting ring shown in FIG. 3,taken at line 4-4 thereof;

FIG. 5 is a view in cross section of the cutting ring element shown inFIG. 3, taken at line 5-5 thereof; and

FIG. 6 is a perspective view of the cutting ring element attached to aback plate and shown in relative position to an impeller having cuttingstructures on the drive side of the impeller to illustrate theinteraction of the cutting ring element to the cutting structures of theimpeller.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates in longitudinal cross section one exemplarconfiguration of a centrifugal chopper pump of the type where thecutting ring element 10 of the present invention is used. Thecentrifugal pump 12 generally comprises a pump casing 14 that is shownin FIG. 1 as comprising a drive casing 16, a volute casing 18 that issecured to the drive casing 16, and a suction casing 20 that is securedto the volute casing 18.

The drive casing 16 is generally structured to receive a drive shaft 22which extends through the drive casing 16 and into the volute casing 18.Bearing assemblies 24 and 26 are generally positioned within the drivecasing 16 to support the drive shaft 22. The drive shaft 22 extendsthrough the drive casing 16 and is attached to the impeller 28, which ispositioned within the volute casing 18.

The drive shaft 22 may also extend through a back plate 30 that ispositioned between the drive casing 16 and impeller 28. The back plate30 is shown secured to an end wall 32 of the drive casing 16, but may besecured to any suitable structure of the pump 12 or portion of the pumpcasing 14. The back plate 30 may be of any suitable configuration thatprovides adjacent positioning of cutting elements to interact with theimpeller 28. The particular back plate 30 illustrated in FIG. 1 isconfigured with an annular collar 34 that extends through the end wall32 of the drive casing 16 and is structured to house a sealing mechanism36 positioned about the drive shaft 22.

In operation of the pump 12, fluid containing larger-sized solids entersinto the pump 12 through an inlet 38 in the suction casing 20. The fluidand solids enter through an intake or chopper plate 40 that ispositioned between the suction casing 20 and the impeller 28. Theimpeller 28 interacts with the chopper plate 40 to cut and chop thesolids in the fluid. The fluid and solids slurry then flows into thevolute 42 of the pump 12 from where it is expelled through the outlet 44of the pump 12.

It can be appreciated from the view of FIG. 1 that as the fluid andsolids slurry moves into the volute 42, the fluid has a tendency toimpact the rear portion 48 of the impeller 28 where it rotates along theback plate 30. It should be noted that the size, dimension and positionof the impeller 28 and back plate 30 as shown in FIG. 1 is merely by wayof example to illustrate the structure of the invention, and the axialextension of the rear portion 48 of the impeller 28 into the volute 42may not be as pronounced as illustrated in FIG. 1. Nonetheless, fluidand debris can move behind the impeller 28, and potentially infiltrateto the drive shaft 22 and sealing mechanism 36 of the pump 12.

Thus, the present invention comprises a cutting ring element 10 which,in association with an impeller 28 having cutting structures 50positioned on the rear portion 48 of the impeller 28, provides cuttingaction of any debris that may initiate entry behind the impeller 28before it can infiltrate to the sealing mechanism 36.

The cutting ring element 10 of the invention is shown in FIG. 1 as beingpositioned on a back plate 30 of the pump 12. This illustration depictsbut one means of positioning and securing the cutting ring element 10adjacent to the impeller 28 and within the pump 12. The cutting ringelement 10 may be attached directly to the pump casing 14, such as tothe drive casing 16 or volute casing 18. The attachment of the cuttingring element 10 to a back plate 30 provides, however, certain advantagesas described more fully hereinafter.

FIGS. 2-4 show more fully the cutting ring element 10, which isgenerally comprised of a ring-like structure 54. The ring-like structure54 has an outer circumferential edge 56 and an inner circumferentialedge 58, and has a radially-extending first surface 60 and an opposing,radially-extending second surface 62. When positioned in a pump, asillustrated in FIG. 1, the second surface 62 is oriented away from theimpeller 28 and is positioned against the backplate 30. The firstsurface 60 is oriented, when positioned in the pump 12, toward theimpeller 28 and is positioned adjacent the impeller 28 as seen inFIG. 1. A plurality of channels 64 extending through the ring-likestructure 54 provide attachment structure, such as for receiving a boltor other fastening device, to secure the cutting ring element 10 to thebackplate 30 or pump casing. Other means of attachment may be equallysuitable.

The ring-like structure 54 is configured with at least one cuttingmember 66 that extends outwardly from the first surface 60 of thering-like structure 54. In the embodiment depicted in FIGS. 2-5, thecutting ring element 10 is constructed with a plurality of cuttingmembers 66. As described more fully hereinafter, the cutting members 66are positioned and configured to interact with cutting structures 50positioned on the drive side of the impeller 28 to effect cutting andchopping of solids that move to the rear portion 48 of the impeller 28.Accordingly, the diameter of the ring-like structure 54 is selected tocoincide with the diameter of the impeller 28 such that the cuttingmembers 66 of the cutting ring element 10 and the cutting structures 50of the impeller 28 are located near the outer periphery of the impeller28, as shown in FIG. 1 and described further below.

The cutting members 66 may be of any suitable size, shape, configurationand number that provides a cutting action in tandem with the cuffingstructures 50 associated with the impeller 28. By way of example only,the cutting members 66 illustrated in FIGS. 2-4 comprise two upwardlyextending cutter teeth 70 which are separated by a slot 72 therebetween;

FIG. 6 best illustrates the positioning of the cutting ring element 10to the impeller 28 and the interaction of the cutting devices associatedwith each. In this view, it can be seen more clearly that the suctionside 76 of the impeller 28 comprises a plurality of vanes 78 whichradiate outwardly from the eye 80 of the impeller 28. In this particularembodiment of an impeller 28, the impeller 28 is formed with a shroud 82which is oriented to be positioned adjacent the back plate 30, ororiented toward the drive side of the pump when assembled in the pump.The vanes 78 extend axially outwardly from the shroud 82 in a directionaway from the back plate 30. The shroud 82 has a circumferential edge 84which defines the periphery of the impeller 28.

The rear surface 88 of the shroud 82 of the impeller 28 is orientedtoward the back plate 30 and is configured with one or more cuttingstructures 50 that are positioned near the periphery of the impeller 28.The cutting structures 50 are sized, shaped and configured in anysuitable manner to intermesh with the cuffing members 66 of the cuttingring element 10. As shown in FIG. 6 by way of example only, the cuttingstructures 50 of the impeller 28 may be comprised of cutter teeth 92which intermesh with the cutter teeth 70 and slot 72 of the cutter ringelement 10. The cutting structures 50 of the impeller 28 may beassociated with expeller vanes extending outwardly from the rear surface88 of the shroud 82.

As further shown in FIG. 6, the second surface 62 of the cutting ringelement 10 is positioned against the front face 94 of the back plate 30and is secured in place by suitable means, such as the positioning ofbolts 96 through the ring-like structure 54 and the back plate 30. Thecutting ring element 10 is sized in diameter so that the cutting members66 are positioned at or near the periphery of the back plate 30 andpositioned to intermesh with the cutting structures 50 located near theperiphery of the impeller 28.

The interaction or intermeshing of the impeller cutter teeth 92 and thecutting members 66 of the cutting ring element 10 provides a cuttingaction on any debris that begins to infiltrate between the rear portion48 of the impeller 28 and the back plate 30. The cutting action, mostimportantly, takes place in proximity to the periphery of the impeller28 and back plate 30, thereby reducing the likelihood that debris willinfiltrate all the way to the center of the impeller 28 near the driveshaft 22 and sealing mechanism 36.

The cutting ring element 10 may be made by casting, machining or by anyother method known in the pump manufacture industry, and is preferablymade of hardened material suitable for pump construction and use,especially use in slurry or chopper type pumps. The cutting ring element10, or at least each cutting member 66 extending from the ring-likestructure 54, is most suitably hardened by known methods in the art torender the cutting members 66 resistant to wear, thereby extending theservice life of the cutting members 66. In normal operation, however,the interaction between the impeller cutter structures 50 and thecutting members 66 of the cutting ring element 10 cause an eventualwearing of both, and a gap forms between the interacting cuttingdevices. The impeller 28 may then be axially adjusted relative to theback plate 30 to lessen the gap between the impeller cutter structures50 and the cutting members 66 of the cutting ring element 10.

Eventually with continued operation, however, the cutter devices of boththe impeller 28 and the cutting ring element 10 become sufficiently wornso that the cutting ring element 10 must be replaced, as well aspossibly the impeller 28. The construction of the cutting ring element10 renders replacement of the cutting members 66 quick and easy, andvery cost effective, over other cutting structures.

The cutting ring element of the present invention is particularly suitedfor use in centrifugal pumps of the chopper type, but may be adapted foruse in any type of centrifugal or slurry pump. Because the configurationof chopper pumps, and centrifugal pumps in general, vary widely, it willbe apparent to those of skill in the art what modifications may berequired to adapt the invention to various pumps. Thus, reference hereinto particularly described or illustrated details of the invention aremerely by way of example and not by way of limitation.

1. A cutting ring element for use in a centrifugal pump, comprising: aring-like structure having a radially-extending first surface fororientation toward an impeller of a pump and an opposing second surfacefor orientation away from an impeller; at least one cutting memberpositioned on said first surface of said ring-like structure; andattachment structure for securing said ring-like structure to a pumpadjacent to an impeller.
 2. The cutting ring element of claim 1 whereinsaid ring-like structure is a continuous circle.
 3. The cutting ringelement of claim 1 wherein said ring-like structure has a diameterselected to position said at least one cutting member in proximity to aperipheral edge of an impeller.
 4. The cutting ring element of claim 1wherein said at least one cutting member comprises spaced apart cutterteeth extending axially outwardly from said first surface.
 5. Thecutting ring element of claim 1 wherein said at least one cutting membercomprises a plurality of cutting members positioned about said ring-likestructure.
 6. The cutting ring element of claim 5 wherein said pluralityof cutting members is each configured with spaced apart cutting teethextending axially outwardly from said first surface of said ring-likestructure.
 7. The cutting ring element of claim 1 wherein said at leastone cutting member is hardened to resist wear.
 8. A centrifugal pumphaving a pump casing and a drive mechanism, comprising: a pump casing;an impeller having a central opening for attachment to a drive mechanismof a pump, a periphery and a drive side, said impeller having at leastone vane radiating outwardly from a central axis of said impeller; atleast one cutting structure positioned on said drive side of saidimpeller located proximate said periphery of said impeller; and acutting ring element having at least one cutting member positionedadjacent said at least one cutting structure of said impeller, said atleast one cutting member being structured and positioned to interactwith said at least one cutting structure of said impeller to effectcutting of solids near the periphery, and on said drive side, of saidimpeller.
 9. The centrifugal pump of claim 8 wherein said cutting ringelement has a diameter selected to position said at least one cuttingmember in proximity to the periphery of said impeller.
 10. Thecentrifugal pump of claim 8 wherein said cutting ring element is securedto said pump casing.
 11. The centrifugal pump of claim 8 furthercomprising a back plate positioned adjacent said drive side of saidimpeller, and wherein said at least one cutting element positionedadjacent said at least one cutting structure of said impeller ispositioned on said back plate.
 12. The centrifugal pump of claim 8wherein said at least one cutting member further comprises a pluralityof cutting members positioned about said cutting ring element andpositioned to interact with said cutting structures of said impeller inproximity to said periphery of said impeller.
 13. The centrifugal pumpof claim 12 wherein each said cutting member further comprises spacedapart cutter teeth extending toward said impeller.